calculateRect.swift

func calculateRectBetween(lastPoint: CGPoint, newPoint: CGPoint) -> CGRect {
    let originX = min(lastPoint.x, newPoint.x) - (lineWidth / 2)
    let originY = min(lastPoint.y, newPoint.y) - (lineWidth / 2)

    let maxX = max(lastPoint.x, newPoint.x) + (lineWidth / 2)
    let maxY = max(lastPoint.y, newPoint.y) + (lineWidth / 2)

    let width = maxX - originX
    let height = maxY - originY

    return CGRect(x: originX, y: originY, width: width, height: height)
}